THERMOSTAT: Probably the most misunderstood component in the cooling system, the thermostat has absolutely nothing to do with controlling maximum engine operating temperature. Period. What does it do? At cold start, it blocks the flow of coolant out of the engine until the trapped coolant reaches the thermostat’s rated temperature, at which point it opens and permits coolant to begin circulating. This aids rapid warm up, which reduces cylinder bore and piston-ring wear by bringing the engine up to operating temperature relatively quickly. Once it’s open, it modulates the flow of coolant through its calibrated restriction so coolant temperature never drops below its rated opening point, assuming the cooling system is efficient enough to cool the engine down to that level. In most cars, it’s essentially wide open all the time, and only the heat transfer efficiency of the radiator and the airflow through the radiator determine the engine’s maximum operating temperature.

If you have a 180º thermostat and your engine operates at 220º, changing to a 160º thermostat won’t change your operating temperature one bit – you need more radiator, more airflow, or both, to reduce operating temperature.

If you have an extremely efficient cooling system with more heat-rejection capability than your engine needs (runs at 180º with a 180º thermostat), changing to a 160º thermostat may result in reducing your operating temperature to 160º, but this is rare except in cold weather. Furthermore, 160º is too cold; OEM testing has proven that the rate of cylinder bore and piston-ring wear at 160º is double the wear rate at 180º, and a coolant temperature of 160º won’t let the oil in the pan get hot enough to boil off condensed moisture and blow-by contaminants, which then remain in suspension and accelerate the formation of acidic sludge. 160º thermostats were specified in the 1930s for the old alcohol-based antifreezes, which would boil off and evaporate at 185º; there’s no other reason for them.

“Balanced-Flow” thermostats like Robertshaw makes (also sold by Mr.Gasket with their name on them) are calibrated much more accurately than conventional parts-store thermostats, and if they fail, they do so in the open position. Conventional thermostats fail closed, which can cause a lot of engine damage in a big hurry if you don’t spot the sudden temperature rise.

Have a great day. On a lighter note, Thank you for your US Army service .

This gets discussed a lot here - and I agree that putting a cooler t-stat on an otherwise stock car is useless - but I've never seen objective (real dyno results, not a butt dyno) that say a 160* t-stat on an otherwise stock car does anything for performance.